Beryllium-copper alloys are notable for their superior combination of thermal conductivity, strength, toughness, impact energy and resistance to corrosion. This has made them desirable for use in control bearings of aircraft landing gear and a variety of underground and undersea applications. Additional benefits of beryllium-copper alloys such as their relatively high electrical conductivity, ultrasonic inspectability and thermal management has made them suitable for face plates of continuous steel casting molds. Aerospace and compact disc technologies have also benefitted, in particular, from the relatively high polishability of these alloys as well as their magnetic transparency, thermal cycling and anti-galling characteristics. The cost of beryllium-copper being an issue, however, more economical processing is sought. Improvements in alloy properties and enhanced product performance are also desired.
In this connection, conventional processing of beryllium-copper alloys have utilized a series of thermal and mechanical treatment steps. For example, a beryllium-copper alloy is cold rolled to heavy reduction, intermediate annealed at temperatures between about 1000.degree. and 1750.degree. F., solution annealed at temperatures of about 1600.degree. to 1850.degree. F., cold rolled to substantially finished gage, then aged at a temperature within a range of about 600.degree. and 1000.degree. F. for less than 1 hour to about 8 hours. An objective is to enhance strength, ductility, formability, conductivity and stress relaxation. A process of this general description may be found, for example, in U.S. Pat. No. 4,565,586 which issued on Jan. 21, 1986 and in U.S. Pat. No. 4,599,120 which issued on Jul. 8, 1986. The disclosures of both patents are hereby incorporated by reference herein.
Although prior methods of processing have been found useful, further improvements in strength and refinements in grain size are desired. For example, finer grain size with uniform equiaxed structure is sought for increased polishability of guidance system mirrors, i.e., to prevent arcing of lasers, and to improve surface quality of molds for manufacturing compact discs. Superior ductility, formability, ultrasonic inspectability and conductivity would ease product manufacture and reduce costs. Further resistance to heat and corrosion is desired to enhance product life and performance, e.g., of control bearings for aircraft landing gear. Moreover, by increasing the fatigue and creep strength of beryllium-copper face plates, performance of steel casting molds would be enhanced.